Accumulated Other Comprehensive (Loss)/Income (Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Nov. 30, 2016 |
Nov. 30, 2015 |
Nov. 30, 2016 |
Nov. 30, 2015 |
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| Accumulated Other Comprehensive (Loss)/Income [Abstract] | ||||
| Beginning balance | $ 39.2 | $ 13.8 | $ 29.2 | $ 7.5 |
| Unrealized (losses)/gains on available-for-sale securities, net of tax | (56.0) | 6.5 | (46.0) | 12.8 |
| Total other comprehensive (loss)/income, net of tax | (56.0) | 6.5 | (46.0) | 12.8 |
| Ending balance | (16.8) | 20.3 | (16.8) | 20.3 |
| Total tax (benefit)/expense included in other comprehensive income | $ (32.0) | $ 3.8 | $ (26.3) | $ 7.4 |
| X | ||||||||||
- Definition Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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